A decarbonized coal power system coupled with a reversible brayton cycle heat pump and a method of operation

Abstract

The application discloses a decarbonization coal power system coupled with a reversible Brayton cycle heat pump and a method thereof, which comprises a coal-fired power generation system for converting heat into electric energy, a decarbonization subsystem for processing carbon dioxide emission, and a heat pump heat storage subsystem for improving energy utilization efficiency; flue gas of a boiler in the coal-fired power generation system enters an absorption tower after passing through a flue gas cooler in the decarbonization subsystem; the coal-fired power generation system sends high-temperature steam generated by the boiler into the heat pump heat storage subsystem through a high-pressure cylinder and a medium-pressure cylinder; and the heat pump heat storage subsystem stores high-temperature molten salt after heat absorption into a high-temperature storage tank. The heat pump heat storage subsystem constructed by the reversible Brayton cycle, which adopts supercritical carbon dioxide as a circulating working medium and phase change materials and molten salt as heat storage mediums, not only improves the energy storage density, but also guarantees the stability and high efficiency of the heat storage and release process, so that the system can better adapt to the fluctuation of power grid load and realize rapid response.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power station decarburization energy storage peak shaving, in particular to a decarburization coal power system coupled with a reversible Brayton cycle heat pump and a method thereof. BACKGROUND

[0002] The power industry is a major source of carbon dioxide emissions, and effective emission reduction measures need to be taken. Carbon capture and storage (CCS) technology after combustion is considered a key means to reduce carbon emissions from coal-fired power plants. Carbon capture technology based on monoethanolamine (MEA) solvent has been widely used due to its mature process, high capture efficiency and low cost.

[0003] However, the MEA carbon capture process requires a large amount of heat energy, while releasing low-grade waste heat. Usually, the heat required by the reboiler comes from the extraction steam of the low-pressure cylinder in the steam turbine, which will significantly reduce the power generation efficiency of the coal-fired power plant and have a certain impact on the safety of the low-pressure cylinder. In addition, with the rapid growth of renewable energy sources such as wind and solar energy with significant time-varying characteristics, the operational flexibility requirements of coal-fired power plants are also increasing. The heat pump heat storage subsystem is a large-scale power storage technology that can achieve electric value-added heating and efficient heat-to-electricity conversion, and is a high-efficiency large-scale energy storage scheme with development potential. Coupling heat pump heat storage technology with carbon capture coal-fired power generation systems can effectively recover low-grade waste heat in carbon capture, and is expected to achieve CO2 emission reduction while reducing energy efficiency penalties, and achieve safe and efficient peak shaving operation of coal-fired power plants. SUMMARY

[0004] This section aims to summarize some aspects of the embodiments of the present application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, abstract and title, and such simplifications or omissions cannot be used to limit the scope of the present application.

[0005] In view of the above or existing problems in the prior art, the present application is proposed.

[0006] Therefore, the purpose of the present application is to provide a decarburization coal power system coupled with a reversible Brayton cycle heat pump and a method thereof, which can effectively reduce the carbon capture energy efficiency penalty in a coal-fired power generation system, further expand the unit peak shaving interval, improve the system operation flexibility, and achieve efficient energy storage and conversion.

[0007] To solve the above technical problems, the present application provides the following technical solutions: a decarbonization coal power system coupled with a reversible Brayton cycle heat pump, which comprises a coal-fired power generation system for converting heat into electric energy, a decarbonization subsystem for processing carbon dioxide emissions, and a heat pump heat storage subsystem for improving energy utilization efficiency; the flue gas of the boiler in the coal-fired power generation system enters the absorption tower after passing through the flue gas cooler in the decarbonization subsystem; the coal-fired power generation system sends the high-temperature steam generated by the boiler to the heat pump heat storage subsystem through the high-pressure cylinder and the medium-pressure cylinder, and the heat pump heat storage subsystem stores the high-temperature molten salt after heat absorption into a high-temperature storage tank.

[0008] As a preferred scheme of the decarbonization coal power system coupled with a reversible Brayton cycle heat pump, the coal-fired power generation system comprises a main steam outlet of the boiler connected with the high-pressure cylinder and a reheated steam outlet of the boiler connected with the medium-pressure cylinder; the coal-fired power generation system further comprises a low-pressure cylinder arranged at the other end of the medium-pressure cylinder, a generator arranged at the other end of the low-pressure cylinder, a condenser connected with the exhaust port of the low-pressure cylinder, and a condensate pump arranged at the other end of the condenser.

[0009] As a preferred scheme of the decarbonization coal power system coupled with a reversible Brayton cycle heat pump, the coal-fired power generation system further comprises a high-pressure heater group connected with the high-pressure steam extraction of the high-pressure cylinder and the medium-pressure cylinder, and a low-pressure heater group connected with the low-pressure steam extraction of the medium-pressure cylinder and the low-pressure cylinder.

[0010] As a preferred scheme of the decarbonization coal power system coupled with a reversible Brayton cycle heat pump, the exhaust steam of the medium-pressure cylinder is divided into three parts, one part is used to heat the feed water of the low-pressure heater group, one part is connected with the steam inlet of the low-pressure cylinder through a throttle valve, and one part enters the heat pump heat storage subsystem through an exhaust port after passing through an adjusting valve; the intermediate steam extraction of the medium-pressure cylinder is divided into three parts, one part is used to heat the feed water of the high-pressure heater group, one part is used to heat the condensate water in the deaerator, and one part enters the small steam turbine through an extraction port.

[0011] As a preferred scheme of the decarbonization coal power system coupled with a reversible Brayton cycle heat pump, the deaerator receives the condensate water from the outlet of the low-pressure heater group and the drain water of the high-pressure heater group, then enters the high-pressure heater group again through a feed water pump, and enters the boiler through the high-pressure heater group.

[0012] As a preferred scheme of the decarbonization coal power system coupled with a reversible Brayton cycle heat pump, the decarbonization subsystem further comprises a rich liquid pump arranged at the bottom of the absorption tower, a lean-rich liquid heat exchanger arranged at the other end of the rich liquid pump, an adsorption tower arranged at the other end of the lean-rich liquid heat exchanger, a reboiler arranged at the bottom of the adsorption tower, a condenser arranged at the top of the adsorption tower, and a steam-water separator arranged at the other end of the condenser; the outlet of the reboiler is further connected with the inlet of the condenser.

[0013] As a preferred solution of the decarbonized coal power system coupled with the reversible Brayton cycle heat pump, wherein: the decarbonized subsystem further comprises a lean liquid cooler arranged at the other end of the lean- rich liquid heat exchanger, and the lean liquid cooler is connected with the absorption tower through a flow collecting valve; the absorption tower is further provided with an absorption tower exhaust cooling pump.

[0014] As a preferred solution of the decarbonized coal power system coupled with the reversible Brayton cycle heat pump, wherein: the heat pump heat storage subsystem comprises a high-temperature storage tank and a low-temperature storage tank; the high-temperature storage tank is connected with the high-temperature heat exchanger hot side inlet through a first valve, and the high-temperature heat exchanger hot side outlet is connected with the low-temperature storage tank inlet; the low-temperature storage tank is connected with the low-temperature heat exchanger cold side inlet through a second valve, and the low-temperature heat exchanger cold side outlet is connected with the high-temperature storage tank inlet.

[0015] As a preferred solution of the decarbonized coal power system coupled with the reversible Brayton cycle heat pump, wherein: the heat pump heat storage subsystem further comprises a first compressor and a second compressor; the first compressor is connected with the first high-temperature regenerator through the low-temperature heat exchanger, the first high-temperature regenerator is connected with the low-temperature regenerator through the first turbine, and the other end of the low-temperature regenerator is connected with the first compressor; the second compressor is connected with the high-temperature heat exchanger through the second high-temperature regenerator, the high-temperature heat exchanger is connected with the cooler through the second turbine, and the other end of the cooler is connected with the second compressor; the hot side outlet of the second high-temperature regenerator is further connected with the main inlet of the ejector; the outlet of the first high-temperature regenerator and the outlet of the ejector are further connected with the inlet of the reboiler; the working medium at the inlet of the first high-temperature regenerator and the working medium at the inlet of the second high-temperature regenerator are both from the exhaust steam of the intermediate pressure cylinder in the coal-fired power generation subsystem; the hot side inlet of the low-temperature regenerator and the inlet of the ejector are further connected with the cold side outlet of the steam-water separator.

[0016] To solve the above technical problems, the present application provides the following technical scheme: a decarbonized coal power operation method coupled with a reversible Brayton cycle heat pump, comprising a decarbonized coal power system coupled with a reversible Brayton cycle heat pump,

[0017] The coal-fired power generation subsystem drives the steam turbine to generate electricity, and part of the steam is extracted for carbon capture and heat pump heat storage subsystem;

[0018] The flue gas of the coal-fired power generation subsystem is cooled and then enters the absorption tower, absorbs CO2 by the MEA solution, releases CO2 by the desorption tower and regenerates the lean liquid, and generates saturated steam by using waste heat;

[0019] The heat storage process of the heat pump heat storage subsystem: using excess power of the power grid to drive the compressor I, compressing and heating the low-temperature working medium, heating the low-temperature molten salt and storing it in the high-temperature storage tank, and converting the electric energy into heat energy;

[0020] Heat release process of heat pump heat storage subsystem: high-temperature molten salt heats working medium, drives turbine II to do work, and the generated mechanical energy is used for power generation to convert thermal energy into electrical energy;

[0021] During heat storage and heat release, the heat from the medium-pressure cylinder extraction steam and part of the heat released by CO2 are mixed by an ejector and then provide heat source for the reboiler in the decarbonization subsystem to desorb CO2.

[0022] The coal-fired power generation subsystem, the decarbonization subsystem, and the heat pump heat storage subsystem are coupled, the medium-pressure cylinder extraction steam is used to heat the heat pump and the reboiler, and the waste heat steam is used to preheat the working medium.

[0023] The heat pump heat storage subsystem constructed by the reversible Brayton cycle realizes efficient energy conversion and storage, has significant environmental protection and economic benefits, and is not limited by geographical conditions, can store heat on a large scale and for a long period, and improves the round-trip efficiency and power density due to the use of supercritical carbon dioxide as the circulating working medium. In addition, the heat pump heat storage subsystem is integrated to effectively recover the waste heat of the MEA carbon capture system, reduce energy waste, provide heat for the reboiler by replacing part of the decarbonization steam, and reduce the energy consumption of the carbon capture process. More importantly, the system can store excess electricity in molten salt during the low electricity consumption period, stabilize the power grid, accommodate new energy, expand the unit peak shaving interval, improve the peak shaving depth, and enhance the stability and flexibility of the power grid. The whole system not only improves the energy utilization efficiency of the coal-fired power plant, but also provides strong support for the stable operation of the power grid and the efficient use of new energy. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative labor. Among them:

[0025] Figure 1 It is a whole structure schematic diagram of the decarbonization coal-fired power system coupled with the reversible Brayton cycle heat pump.

[0026] Figure 2 It is a partial structure schematic diagram of the decarbonization coal-fired power system coupled with the reversible Brayton cycle heat pump.

[0027] Figure 3 It is a partial structure schematic diagram of the decarbonization coal-fired power system coupled with the reversible Brayton cycle heat pump.

[0028] Figure 4 It is a whole flow schematic diagram of the decarbonization coal-fired power operation method coupled with the reversible Brayton cycle heat pump. DETAILED DESCRIPTION

[0029] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, specific embodiments of the present application will be described in detail below with reference to the accompanying drawings.

[0030] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application, however, can be practiced in a variety of ways other than those specifically described herein, and the scope of the present application is not limited to the specific embodiments described herein.

[0031] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. "In one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments.

[0032] Embodiment 1

[0033] Reference Figure 1 For the first embodiment of the present application, the embodiment provides a decarbonized coal power system coupled with a reversible Brayton cycle heat pump, which includes a coal-fired power generation system 100 for converting heat into electrical energy, a decarbonization subsystem 200 for processing carbon dioxide emissions, and a heat pump heat storage subsystem 300 for improving energy utilization efficiency.

[0034] Specifically, the exhaust gas of the boiler 101 in the coal-fired power generation system 100 enters the absorption tower 202 after passing through the flue gas cooler 201 in the decarbonization subsystem 200; the coal-fired power generation system 100 sends the high-temperature steam generated by the boiler 101 to the heat pump heat storage subsystem 300 through the high-pressure cylinder 102 and the medium-pressure cylinder 103.

[0035] It should be noted that the heat pump of the heat pump heat storage subsystem 100 adopts a reversible Brayton cycle, with a COP greater than 4.0, and the working medium of the reversible Brayton heat pump cycle is supercritical carbon dioxide, with a high power density and a high round-trip efficiency.

[0036] It should be noted that the boiler 101 of the coal-fired power generation system 100 is a circulating fluidized bed boiler, with an operating temperature of 900℃ and a pressure of 25MPa, and a combustion efficiency of more than 90%.

[0037] It should be noted that the inlet steam temperature of the high-pressure cylinder is 550℃, and the pressure is 17MPa; the inlet steam temperature of the medium-pressure cylinder is 450℃, and the pressure is 10MPa.

[0038] It should be noted that the high-temperature steam generated by the boiler 101 has a temperature of 500℃ and a pressure of 12MPa. The exhaust smoke is cooled by the indirect contact smoke-steam cooler 201 in the decarburization subsystem 200, and the cooling efficiency is greater than 90%. After cooling, the temperature of the exhaust smoke is reduced to 150℃ and then enters the absorption tower 202.

[0039] It should be noted that the absorption tower 202 uses ceramic filler, and the CO2 absorption efficiency reaches 96%. The high-temperature steam is sent to the heat pump heat storage subsystem 300, and the COP of the heat pump is 4.2. The heat storage medium is a phase change material, and the phase change temperature is 350℃.

[0040] It should be noted that the heat storage medium used in the heat pump heat storage subsystem 300 is molten salt, and the working temperature range of the molten salt is 300℃ to 400℃, which effectively guarantees the energy storage efficiency.

[0041] In summary, the system of the present application improves the energy conversion efficiency and reduces environmental pollution by efficient combustion of the boiler, efficient cooling and CO2 absorption of the exhaust smoke, effective utilization of high-temperature steam, and high COP and phase change heat storage of the heat pump heat storage subsystem. The system effectively realizes the improvement of energy utilization efficiency and the reduction of CO2 emission. The system uses supercritical carbon dioxide as the working medium, which realizes a high COP value of 4.2, which means that the system can output more heat energy with less power consumption, significantly improving the energy utilization efficiency. The system also uses phase change materials and molten salts as heat storage media, which not only improves the energy storage density, but also guarantees the stability and efficiency of the heat storage process, so that the system can better adapt to the fluctuation of power grid load and realize fast response.

[0042] Embodiment 2

[0043] Reference Figures 1-2 For the second embodiment of the present application, the embodiment provides a decarburization coal-fired power system coupled with a reversible Brayton cycle heat pump, which comprises a coal-fired power generation subsystem 100 and a decarburization subsystem 200 that work together to improve the energy utilization efficiency, and reduces the carbon dioxide emission in the coal-fired power generation process through the decarburization effect of the absorption tower 202.

[0044] Specifically, the coal-fired power generation subsystem 100 comprises a main steam outlet of the boiler 101 connected with the high-pressure cylinder 102, and a reheat steam outlet of the boiler 101 connected with the medium-pressure cylinder 103. The coal-fired power generation subsystem 100 further comprises a low-pressure cylinder 104 arranged at the other end of the medium-pressure cylinder 103, a generator 105 arranged at the other end of the low-pressure cylinder 104, a condenser 106 connected with the exhaust port of the low-pressure cylinder 104, and a condensate pump 107 arranged at the other end of the condenser 106.

[0045] Specifically, the coal-fired power generation system 100 further comprises a high-pressure heater group 108 connected with the high-pressure extraction of the high-pressure cylinder 102 and the intermediate-pressure cylinder 103, and a low-pressure heater group 109 connected with the low-pressure extraction of the intermediate-pressure cylinder 103 and the low-pressure cylinder 104.

[0046] It should be noted that the feed water enters the boiler 101, and after generating the main steam, enters the high-pressure cylinder 102. Part of the intermediate extraction of the high-pressure cylinder 102 is used to heat part of the feed water of the high-pressure heater group 108, and the exhaust steam of the high-pressure cylinder 102 is returned to the boiler 101 for heating, generating reheat steam, and then entering the intermediate-pressure cylinder 103.

[0047] It should be noted that part of the intermediate extraction of the low-pressure cylinder 104 is used to heat part of the feed water of the low-pressure heater group 109.

[0048] It should be noted that the high-pressure cylinder 102, the intermediate-pressure cylinder 103, and the low-pressure cylinder 104 are coaxially connected, and the mechanical energy generated is transmitted to the generator 105 to output electric energy.

[0049] Specifically, the exhaust steam of the intermediate-pressure cylinder 103 is divided into three parts, one part is used to heat part of the feed water of the low-pressure heater group 109, one part is connected with the steam inlet of the low-pressure cylinder 104 through the throttle valve 110, and one part passes through the adjusting valve 111 and enters the heat pump heat storage subsystem 300 through the exhaust port Z; the intermediate extraction of the intermediate-pressure cylinder 103 is divided into three parts, one part is used to heat part of the feed water of the high-pressure heater group 108, one part is used to heat the condensate water in the deaerator 112, and one part enters the small steam turbine 114 through the extraction port X.

[0050] Further, the inlet steam of the small steam turbine 114 comes from the extraction of the intermediate-pressure cylinder 103, and the steam outlet of the small steam turbine 114 is also connected with the steam inlet of the condenser 106.

[0051] Specifically, after the deaerator 112 receives the condensate water from the outlet of the low-pressure heater group 109 and the drain of the high-pressure heater group 108, it enters the high-pressure heater group 108 again through the feed water pump 113, and then enters the boiler 101 through the high-pressure heater group 108.

[0052] Specifically, the decarburization subsystem 200 further comprises a rich liquid pump 203 arranged at the bottom of the absorption tower 202, a lean-rich liquid heat exchanger 204 arranged at the other end of the rich liquid pump 203, the other end of the lean-rich liquid heat exchanger 204 connected with a desorption tower 205, a reboiler 206 arranged at the bottom of the desorption tower 205, a condenser 207 arranged at the top of the desorption tower 205, and a steam-water separator 208 arranged at the other end of the condenser 207; the outlet of the reboiler 206 is also connected with the inlet of the condenser 106.

[0053] Further, the cold side outlet of the steam-water separator 208 is connected with the hot side inlet of the low temperature recuperator 311 and the injection inlet of the ejector 315 in the heat pump heat storage subsystem 300.

[0054] It should be noted that the flue gas outlet temperature of the smoke steam cooler 201 is reduced to 150℃.

[0055] It should be noted that the MEA solvent circulation amount of the absorption tower 202 is 2000 liters per hour, and the CO2 absorption efficiency reaches 95%. The main fluid pressure is 0.35 MPa, and the mixed gas stream pressure is stabilized at 0.3 MPa by the injection of waste heat steam.

[0056] Specifically, the decarbonization subsystem 200 further comprises a lean liquid cooler 209 arranged at the other end of the lean-rich liquid heat exchanger 204 and connected with the absorption tower 202 through a flow collecting valve 210; and the absorption tower 202 is further provided with an absorption tower exhaust cooling pump 211.

[0057] It should be noted that the lean liquid cooler 209 heats a stream of 25℃ industrial water by carbon capture waste heat to form a stream of saturated steam, which reduces the extraction of the medium pressure cylinder 1033 in the heat release process, effectively reducing the energy efficiency penalty.

[0058] The flue gas treatment process of the decarbonization subsystem 200 is as follows:

[0059] The flue gas generated by the boiler 101 is cooled in the smoke steam cooler 201 after treatment, and then enters the absorption tower 202 to be absorbed by the MEA solvent to form a rich liquid, which enters the lean-rich liquid heat exchanger 204 through the rich liquid pump 203, and then enters the desorption tower 205 after being heated, and forms a mixture of carbon dioxide and water vapor under the action of the reboiler 206, and then passes through the condenser 207 and the steam-water separator 208 in sequence;

[0060] The lean liquid at the bottom of the desorption tower 205 passes through the lean-rich liquid heat exchanger 204 and the lean liquid cooler 209 in sequence, and the temperature is reduced, and then enters the absorption tower 202 together with the supplemented MEA and water through the flow collecting valve 210 to complete the circulation;

[0061] The waste heat recovery process is that a stream of 25℃ feed water passes through the lean liquid cooler 209, the smoke steam cooler 201, the absorption tower exhaust cooling pump 211 and the steam-water separator 208 in sequence to exchange heat, and finally forms a stream of saturated steam.

[0062] The condensate water of the reboiler 206, the exhaust steam of the small steam turbine 114, the exhaust steam of the low-pressure cylinder 104, and the drain of the low-pressure heater group 109 are combined into the condenser 106 to condense and generate condensate water, which is pumped by the condensate pump 107 into the low-pressure heater group 109. The condensate water at the outlet of the low-pressure heater group 109 and the drain from the high-pressure heater group 108 are combined into the deaerator 112. After the deaerator 112 generates saturated feed water, part of the saturated feed water is introduced into the heat pump heat storage subsystem 300, and part of the saturated feed water is pumped by the feed water pump 113 into the high-pressure heater group 108, and then into the boiler 101. After the boiler 101 generates new steam, the new steam is introduced into the high-pressure cylinder 102, and the process is repeated.

[0063] In summary, the present application significantly improves energy utilization efficiency and reduces CO2 emissions by optimizing the synergistic effect of the coal-fired power generation system and the decarbonization subsystem. The main steam and reheat steam generated by the boiler are introduced into the high-pressure cylinder and the intermediate-pressure cylinder, respectively, and the mechanical energy is transmitted to the generator through the coaxially connected cylinder body, thereby improving the energy conversion efficiency. The reasonable distribution of the intermediate-pressure cylinder exhaust steam and the utilization of the intermediate extraction steam achieve efficient heat energy management of the heater group and the deaerator. The decarbonization subsystem absorbs CO2 in the flue gas through the MEA solvent in the absorption tower, forms a rich liquid, and finally releases a mixed gas of CO2 and water vapor, significantly reducing the carbon dioxide emissions in the coal-fired power generation process. The MEA solvent circulation amount is 2000 liters per hour, and the CO2 absorption efficiency reaches 95%. The use of regulating valves and throttling valves enhances the peak shaving capability, and the small steam turbine allows part of the extraction steam to be directly used for power generation, thereby improving the energy utilization flexibility of the system. The waste heat recovery equipment such as the lean liquid cooler uses the waste heat of carbon capture to heat industrial water to form saturated steam, effectively utilizing the otherwise wasted heat energy, reducing the extraction demand of the intermediate-pressure cylinder, reducing the energy efficiency penalty, and improving the overall energy utilization efficiency. These technical steps provide an efficient and environmentally friendly coal-fired power generation solution, effectively promoting the sustainable development of the energy industry.

[0064] Embodiment 3

[0065] Reference Figures 1-3 For the third embodiment of the present application, the embodiment provides a decarbonized coal power system coupled with a reversible Brayton cycle heat pump, which includes heat transfer from a low-temperature heat source to a high-temperature heat source through a heat pump heat storage subsystem 300, thereby improving the energy utilization efficiency of the entire system.

[0066] Specifically, the heat storage module heat pump heat storage subsystem 300 includes a high-temperature storage tank 301 and a low-temperature storage tank 302. The high-temperature storage tank 301 is connected to the hot side inlet of the high-temperature heat exchanger 304 through the first valve 305, and the hot side outlet of the high-temperature heat exchanger 304 is connected to the inlet of the low-temperature storage tank 302. The low-temperature storage tank 302 is connected to the cold side inlet of the low-temperature heat exchanger 306 through the second valve 303, and the cold side outlet of the low-temperature heat exchanger 306 is connected to the inlet of the high-temperature storage tank 301.

[0067] Further, the high-temperature storage tank 301, the low-temperature storage tank 302, the first valve 303, the high-temperature heat exchanger 304, the second valve 305 and the low-temperature heat exchanger 306 constitute a closed-loop heat energy storage and release module in the heat pump heat storage subsystem 300.

[0068] It should be noted that the heat storage medium used in the high-temperature storage tank 301 and the low-temperature storage tank 302 is molten salt.

[0069] Specifically, the heat pump heat storage subsystem 300 further includes a first compressor 307 and a second compressor 308; the first compressor 307 is connected with a first high-temperature regenerator 309 through the low-temperature heat exchanger 306, the first high-temperature regenerator 309 is connected with a low-temperature regenerator 311 through a first turbine 310, and the other end of the low-temperature regenerator 311 is connected with the first compressor 307; the second compressor 308 is connected with the high-temperature heat exchanger 304 through a second high-temperature regenerator 312, the high-temperature heat exchanger 304 is connected with a cooler 314 through a second turbine 313, and the other end of the cooler 314 is connected with the second compressor 308; the hot side outlet of the second high-temperature regenerator 312 is also connected with the main inlet of an ejector 315; the outlet of the first high-temperature regenerator 309 and the outlet of the ejector 315 are also connected with the inlet of the reboiler 206; the inlet working medium of the first high-temperature regenerator 309 and the inlet working medium of the second high-temperature regenerator 312 are both from the exhaust steam of the intermediate-pressure cylinder 103 in the coal-fired power generation system 100; the hot side inlet of the low-temperature regenerator 311 and the inlet of the ejector 315 are also connected with the cold side outlet of the steam-water separator 208.

[0070] Further, the first compressor 307, the second compressor 308, the first high-temperature regenerator 309, the first turbine 310, the low-temperature regenerator 311, the second high-temperature regenerator 312, the second turbine 313, the cooler 314 and the ejector 315 constitute a heat pump module of a reversible Brayton cycle in the heat pump heat storage subsystem 300.

[0071] It should be noted that the inlet working medium pressure of the first compressor 307 and the second compressor 308 is 8-10 MPa, and the outlet working medium pressure is 25-30 MPa. The inlet working medium pressure of the main compressor is maintained above the critical point to keep the entire cycle in a supercritical state.

[0072] It should be noted that the inlet working medium temperature of the first high-temperature regenerator 309 and the second high-temperature regenerator 312 is 120℃, and the outlet working medium temperature is 300℃.

[0073] It should be noted that the main fluid of the ejector 315 is steam with a pressure greater than 0.3 MPa, and the mixed gas flow pressure is 0.3 MPa by using the waste heat steam to ensure that the heating steam entering the reboiler 206 has stable pressure, thereby improving the safety and economy of the system.

[0074] The heat storage process of the heat pump heat storage subsystem 300: the second valve 305 is opened, the first valve 303 is closed, the first compressor 307 is driven by using the excess power of the power grid to compress the carbon dioxide working medium at the low-temperature heat regenerator 311 outlet to a high-temperature and high-pressure state, then the heat is transferred to the low-temperature molten salt in the low-temperature heat exchanger 306, the high-temperature molten salt after absorbing heat is stored in the high-temperature storage tank 301, the carbon dioxide at the hot side outlet of the low-temperature heat exchanger 306 enters the first high-temperature heat regenerator 309 to absorb the heat from the steam extracted from the intermediate-pressure cylinder 103, then enters the first turbine 310 to do work, and enters the first compressor 307 after absorbing the heat of the waste heat steam in the low-temperature heat regenerator 311 to complete the cycle. Therefore, the charging process is to convert the excess power into high-grade heat energy and store it in the high-temperature storage tank.

[0075] The heat release process of the heat pump heat storage subsystem 300: the first valve 303 is opened, the second valve 305 is closed, the high-temperature and high-pressure carbon dioxide working medium from the high-temperature heat exchanger 304 enters the second turbine 313 to do work, then enters the cooler 314 to release heat, and then enters the second compressor 308, the working medium at the outlet of the second compressor 308 enters the second high-temperature heat regenerator 312 cold side and the high-temperature heat exchanger 304 cold side in turn to absorb heat, and completes the cycle; therefore, the heat release process is to convert the stored high-grade heat energy into electrical energy according to the demand of the power grid.

[0076] In summary, the system can convert the excess electrical energy into high-grade heat energy for storage during the low electricity consumption period, and convert the stored heat energy back into electrical energy during the peak period, thereby improving the peak shaving capacity and energy utilization efficiency of the system. In addition, the system effectively recovers the waste heat of the MEA carbon capture system, reduces the energy efficiency penalty of the carbon capture process, and realizes safe and efficient peak shaving operation of the coal-fired power plant.

[0077] Embodiment 4

[0078] With reference to Figure 4 , the fourth embodiment of the present application provides a decarbonized coal power operation method coupled with a reversible Brayton cycle heat pump, which comprises.

[0079] The steam turbine is driven by the coal-fired power generation system to generate electricity, and part of the steam is extracted for carbon capture and heat pump heat storage subsystem;

[0080] The flue gas of the coal-fired power generation system enters the absorption tower after being cooled, absorbs CO2 by the MEA solution, releases CO2 in the desorption tower and regenerates the lean solution, and generates saturated steam by using waste heat;

[0081] The heat storage process of the heat pump heat storage subsystem: the compressor I is driven by using the excess power of the power grid to compress and heat the low-temperature working medium, heat the low-temperature molten salt and store it in the high-temperature storage tank, and convert the electrical energy into heat energy;

[0082] The heat releasing process of the heat pump heat storage subsystem: the high-temperature molten salt heats the working medium, drives turbine II to do work, and the mechanical energy generated is used for power generation to convert thermal energy into electrical energy;

[0083] During the heat storage and heat releasing processes, the heat from the medium-pressure cylinder extraction steam and part of the heat released by CO2 are mixed by the ejector and then provide heat source for the reboiler in the decarbonization subsystem to desorb CO2;

[0084] The coal-fired power generation subsystem, the decarbonization subsystem, and the heat pump heat storage subsystem are coupled, the medium-pressure cylinder extraction steam is used to heat the heat pump and the reboiler, and the waste heat steam is used to preheat the working medium.

[0085] Importantly, it should be appreciated that the constructions and arrangements of the present application shown in the various different example embodiments are merely illustrative. Although only a few embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter described in this application. For example, elements shown as integrally formed can be constructed of multiple parts or elements, the position of elements can be reversed or otherwise varied, and the nature or number of elements or positions can be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present application. The order or sequence of any process or method steps can be changed or re-sequenced without departing from the generality of the application. In the claims, any means-plus-function clause is intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Other substitutions, modifications, changes, and omissions can be made in the design, operating conditions, and arrangement of the example embodiments without departing from the scope of the present application. Accordingly, the present application is not limited to particular embodiments described, but extends to various modifications that nevertheless fall within the scope of the appended claims.

[0086] Furthermore, in order to provide a concise description of the exemplary embodiments, all features of an actual implementation can not be described (i.e., those unrelated to the best mode of practicing the present application currently contemplated).

[0087] It is understood that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions can be made. Such development efforts might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

[0088] It should be noted that the above examples are only used to illustrate the technical solutions of the present application but not limit the present application. Although the present application is described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or equivalently replaced, without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump, characterized in that: include, A coal-fired power generation system (100) that converts heat into electricity, a decarbonization subsystem (200) for treating carbon dioxide emissions, and a heat pump thermal storage subsystem (300) for improving energy efficiency. The flue gas from the boiler (101) in the coal-fired power generation system (100) enters the absorption tower (202) after passing through the flue gas cooler (201) in the decarbonization subsystem (200). The coal-fired power generation system (100) sends the high-temperature steam generated by the boiler (101) into the heat pump heat storage subsystem (300) through the high-pressure cylinder (102) and the medium-pressure cylinder (103). The heat pump heat storage subsystem (300) stores the heat-absorbing high-temperature molten salt in the high-temperature storage tank (301). The coal-fired power generation system (100) includes a main steam outlet of a boiler (101) connected to a high-pressure cylinder (102) and a reheat steam outlet of the boiler (101) connected to a medium-pressure cylinder (103); The coal-fired power generation system (100) also includes a low-pressure cylinder (104) at the other end of the intermediate-pressure cylinder (103), a generator (105) at the other end of the low-pressure cylinder (104), a condenser (106) connected to the exhaust port of the low-pressure cylinder (104), and a condensate pump (107) at the other end of the condenser (106). The coal-fired power generation system (100) further includes a high-pressure heater group (108) connected to the high-pressure steam extraction of the high-pressure cylinder (102) and the intermediate-pressure cylinder (103), and a low-pressure heater group (109) connected to the low-pressure steam extraction of the intermediate-pressure cylinder (103) and the low-pressure cylinder (104). The exhaust steam of the intermediate pressure cylinder (103) is divided into three paths: one path is used to heat part of the feed water of the low pressure heater group (109); another path is connected to the steam inlet of the low pressure cylinder (104) through the throttle valve (110); and the third path passes through the regulating valve (111) and enters the heat pump heat storage subsystem (300) through the exhaust port (Z). The intermediate steam extraction of the intermediate pressure cylinder (103) is divided into three paths: one path is used to heat part of the feedwater of the high pressure heater group (108), one path is used to heat the condensate in the deaerator (112), and one path enters the small steam turbine (114) through the extraction port (X). The deaerator (112) receives condensate from the outlet of the low-pressure heater group (109) and condensate from the high-pressure heater group (108), and then re-enters the high-pressure heater group (108) through the feed water pump (113), and then enters the boiler (101) through the high-pressure heater group (108). The decarbonization subsystem (200) further includes a rich liquid pump (203) at the bottom of the absorption tower (202), a lean-rich liquid heat exchanger (204) at the other end of the rich liquid pump (203), a desorption tower (205) at the other end of the lean-rich liquid heat exchanger (204), a reboiler (206) at the bottom of the desorption tower (205), a condenser (207) at the top of the desorption tower (205), and a steam-water separator (208) at the other end of the condenser (207). The outlet of the reboiler (206) is also connected to the inlet of the condenser (106); The decarbonization subsystem (200) also includes a lean liquid cooler (209) provided at the other end of the lean and rich liquid heat exchanger (204), and the lean liquid cooler (209) is connected to the absorption tower (202) through a manifold valve (210); The absorption tower (202) is also equipped with an absorption tower exhaust cooling pump (211). The heat pump thermal storage subsystem (300) includes a high-temperature storage tank (301) and a low-temperature storage tank (302). The high-temperature storage tank (301) is connected to the hot-side inlet of the high-temperature heat exchanger (304) through the first valve (303), and the hot-side outlet of the high-temperature heat exchanger (304) is connected to the inlet of the low-temperature storage tank (302). The cryogenic storage tank (302) is connected to the cold side inlet of the cryogenic heat exchanger (306) through the second valve (305), and the cold side outlet of the cryogenic heat exchanger (306) is connected to the inlet of the high temperature storage tank (301). The heat pump storage subsystem (300) also includes a first compressor (307) and a second compressor (308); The first compressor (307) is connected to the first high-temperature regenerator (309) through a low-temperature heat exchanger (306), the first high-temperature regenerator (309) is connected to the low-temperature regenerator (311) through a first turbine (310), and the other end of the low-temperature regenerator (311) is connected to the first compressor (307). The second compressor (308) is connected to the high-temperature heat exchanger (304) through the second high-temperature regenerator (312), the high-temperature heat exchanger (304) is connected to the cooler (314) through the second turbine (313), and the other end of the cooler (314) is connected to the second compressor (308). The hot-side outlet of the second high-temperature regenerator (312) is also connected to the main inlet of the ejector (315); The outlet of the first high-temperature regenerator (309) and the outlet of the ejector (315) are also connected to the inlet of the reboiler (206); The inlet working medium of the first high-temperature regenerator (309) and the inlet working medium of the second high-temperature regenerator (312) both come from the exhaust steam of the intermediate-pressure cylinder (103) in the coal-fired power generation system (100); The hot-side inlet of the low-temperature regenerator (311) and the inlet of the ejector (315) are also connected to the cold-side outlet of the steam-water separator (208).

2. A method for operating a decarbonized coal-fired power plant coupled with a reversible Brayton cycle heat pump, characterized in that: The decarbonized coal-fired power system coupled with a reversible Brayton cycle heat pump as described in claim 1; and, The system generates electricity by driving a steam turbine through a coal-fired power generation system, and extracts some steam for carbon capture and heat pump storage subsystems. After being cooled, the flue gas from the coal-fired power generation system enters the absorption tower, where CO2 is absorbed by the MEA solution. The desorption tower releases CO2 and regenerates the lean liquor, using the waste heat to generate saturated steam. The heat storage process of the heat pump heat storage subsystem: using surplus electricity from the power grid to drive compressor I, compressing and heating the low-temperature working fluid, heating the low-temperature molten salt and storing it in a high-temperature storage tank, converting electrical energy into heat energy; The heat release process of the heat pump heat storage subsystem: the high-temperature molten salt heats the working fluid, drives turbine II to do work, and the mechanical energy generated is used to generate electricity, converting thermal energy into electrical energy; During the heat storage and release process, the heat from the steam extracted from the intermediate pressure cylinder and part of the heat released by CO2 are mixed by the ejector and together provide a heat source for the reboiler in the decarbonization subsystem for the desorption of CO2. The system couples the coal-fired power generation system, the decarbonization subsystem, and the heat pump thermal storage subsystem. It uses steam extraction from the intermediate-pressure cylinder to supply heat to the heat pump and reboiler, and utilizes waste heat steam to preheat the working fluid.

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